With rapid development of machine-to-machine (Full name: Machine to Machine, M2M for short) communications applications, market requirements and the market scale explosively grow. An M2M communications application has a service requirement different from that of a conventional communications service, such as deep coverage and low power consumption. The following solution is put forward for the service requirement of the M2M communications application: After receiving downlink data sent by a base station on a physical downlink shared channel (Full name: Physical Downlink Shared Channel, PDSCH for short), a terminal device needs to provide feedback for the downlink data. If the terminal device successfully receives the downlink data, the terminal device feeds back an acknowledgement (Full name: Acknowledgement, ACK for short); or if the terminal device fails to receive the downlink data, the terminal device feeds back a negative acknowledgement (Full name: Negative Acknowledgement, NACK for short). For example, a data transmission process may be shown in FIG. 1.
Currently, in the data transmission process in FIG. 1, a time-frequency resource location of downlink feedback information is mainly mapped by using a time-frequency resource location of a physical downlink control channel (Full name: Physical Downlink Control Channel, PDCCH for short), so that the time-frequency resource location of the downlink feedback information is determined, and the downlink data sent on the PDSCH is fed back at the time-frequency resource location of the downlink feedback information.
However, for a system in which cross-PDCCH scheduling is performed, if the time-frequency resource location of the downlink feedback information is mapped by using the time-frequency resource location of a PDCCH, a resource conflict may occur because feedback is provided for multiple pieces of the downlink data at a same time-frequency resource location of the downlink feedback information. Consequently, the base station cannot correctly receive the downlink feedback information sent by a terminal device, and a transmission success rate of the downlink feedback information is not high.